IdentificationWhile usually green, this species can also have reddish-brown or purplish spines. The spines are relatively short (to 2.5 cm long) and fine, and are all similar in length. The tube feet are purplish, and darker than the spines. This species reaches about 9 cm in diameter. Its diameter is less than twice its thickness.

Habitat & RangeThis species prefers habitats protected from direct surge, such as sheltered rocky reefs and kelp beds. It inhabits the intertidal and subtidal to depths of 1140 m. The green sea urchin has a northern, but not circumpolar, distribution around the world. On the Pacific coast of North America its range extends from Alaska to Puget Sound, Washington. It is also found along the Pacific coastline of Russia, and North Atlantic coastlines in Europe.

Human UsesThe roe (actually reproductive organs, not eggs) of sea urchins is a delicacy in Japan, where they are called uni, and they are commercially harvested for this purpose. Maine became a massive exporter of sea urchins on the east coast in the 1990s, but populations were overharvested and have been slow to recover. Click here to read more.

Intriguing InfoSea urchins, sea otters, and bull kelp (Nereocystis leutkeana) are intimately tied together. When sea otters — which prey on urchins — are absent, sea urchin populations can rise to levels where they can devastate kelp forests. These "deforested" areas of ocean floor are known as 'urchin barrens,' where the productive kelp forest habitat is absent. Sea otters were absent along much of the west coast until very recently, as a result of overhunting in the 18th and 19th centuries. For more on the role of sea urchins and kelp forests, see this article.